In the rest of the present specification, the invention will be described in reference to beverages preparation, more particularly coffee. However, this should not be taken as limiting the scope of the present specification and claims. The present invention is generally directed to the preparation of any food or nutritional product that can be prepared by injection of a fluid into a capsule or pod in a food preparation machine, and which involves a high fluid pressure inside the capsule to extract or dissolve the ingredient(s) contained therein. Such food or nutritional products can include for instance soluble coffee and/or powdered roast and ground coffee beans, dairy products, such as milk preparation, infant milk, soups, ice cream, chocolate-based products, teas or herbal infusions, semi-liquid or liquid desserts.
Capsules containing a substance for the preparation of beverages such as coffee, by extraction or mixing at high pressure are well known, particularly in the domain of espresso coffee, or soluble coffee preparation, and are particularly interesting from a hygiene perspective, as well as for the product freshness it guarantees. Consumer friendliness and ease of preparation is also a particular advantage of such systems.
The capsules may be closed capsules serving as a chamber for the injection of water and opening in order to release the liquid beyond a certain pressure threshold by means of the rupturing of a face of the capsule in contact with elements that are in relief. Alternatively, some capsules are used which comprise fluid inlet and/or product outlet openings which are pre-existing at the time the user introduces the said capsule into the food preparation machine.
Water is usually injected by means of perforation through the capsule using a needle or spikes. An example of an extraction system of this type is described in Patent EP 0 512 470 B1 or, alternatively, EP 0 870 457. In another possible alternative, the capsule has its own release-type means for rupturing a capsule film or membrane and thereby releasing the liquid extract when a pressure threshold has been achieved inside the capsule.
The capsules may also be permeable chambers of the filter type or, alternatively, semi-permeable chambers comprising a filter component.
In all cases, internal pressure in the capsule chamber is a main driver for the creation of foam in dissolution products and for the creation of cream—or crema—for powdered roast and ground coffee. It is also the main driver for creation of crema in ground coffee extraction. Crema is very important for consumers as it provides controlled aroma release as well as for its own mouth feel.
It is known to use substances to be mixed (soluble or dispersible substances) and substances to be extracted under pressure using the same machine so as to offer a wider variety of beverages. For example, on using one and the same machine, it is possible to prepare an “espresso” coffee when the capsule contains a ground coffee, as well as a cappuccino.
The injection, mixing or wetting conditions have a considerable influence on the quality of the beverage produced. Depending on whether a substance, resulting from grinding, pressed down into a capsule is involved, or, alternatively, a substance to be dissolved or dispersed in a liquid, such as a soluble coffee or a milk-based substance such as a cappuccino, or the like is involved, the way in which the water circulates through the capsule has an influence on the extraction or mixing conditions and thus on the final quality of the beverage.
Thus, a product such as coffee has to be dissolved or dispersed rapidly and completely, producing preferably foam with a specific texture. In the case of products to be extracted, such as ground coffee, the optimum wetting conditions are different. The product must be thoroughly wetted, thereby optimizing the water/coffee contact surface, without creating preferred routes for the water through the bed of coffee. The creation of a privileged route through the bed of coffee may result in too sudden an increase in pressure and thus too rapid a release of the extract despite the fact that the extraction time is insufficient and part of the coffee has not yet been correctly wetted.
There is a need for a capsule wherein the flow of product through the capsule outlet when said capsule is open, is controlled so that the pressure inside the capsule is kept at a consistent level during the whole extraction and/or dissolution step, while still allowing a proper dispensing of the product.